Seasonal dynamics of dominant species of soil predators (Coleoptera, Staphylinidae, Carabidae) in agrolandscapes and their potential gluttony Fazlitdin Halimov

Potential gluttony

The trophic connections of carnivorous beetles on vegetable fields are very wide. Smaller species of ground beetles prefer to eat eggs and larvae of I-II phases of harmful insects (cabbage flies, scoops), and larger ones - adult pest larvae. However, the latter, due to a hidden lifestyle (some are located on the apical part of plants), are usually inaccessible to predatory ground beetles, while egg clutches lying more openly are more easily detected by them.

Small species of ground beetles, primarily bembidions and staphilins, are most active in the search and extermination of egg-laying pests. Their role is especially high in the extermination of eggs and larvae of younger ages of pests in the first period of plant vegetation, when specialized entomophages are absent on the fields of vegetable crops. Bembidions (B.properans, B.quadimaculatum, B.femoratum) and some staphylins (A.bilineata, Aloconota gregaria) are pronounced predators and willingly feed on eggs and pest larvae. Although some authors (Ball et al., 2015, Michael et al., 2017) believe that larger species of predators are most effective in exterminating larvae and pupae of pests, it seems to us that small species, destroying pest eggs, make a more significant contribution to biological control, since the destruction of pests in earlier periods of their development is more important from an economic point of view.

Ground beetles, prevailing in numbers during the second period of plant vegetation (H. rufipes and species of the genus Amara) have a mixed type of nutrition. There are different opinions on the value of ground beetles with a mixed type of nutrition in the literature. While some authors attribute them as harmful species (Kryzhanovsky, 1974), others consider them useful (Razumov, 1983). In the field, we did not observe damage to plants by these bugs. And in the laboratory, these beetles willingly ate the larvae of the cabbage flies.

A very difficult task is to consider the effectiveness of predators in the field. To clarify the role of predators in the extermination of eggs and larvae of pests in laboratory conditions, a series of experiments were conducted. In the first series of experiments, beetles were kept in Petri dishes on moistened filter paper. The most voracious was staphilin Aleochara bilineata. With the number of 20 eggs of the pest, the beetles completely destroyed them per day. And with the number of 50 and 100 eggs of the pest, the beetles consumed, on average, 45.66 and 82 eggs per day, respectively (Figure 3).

Among ground beetles, larger species, Harpalus rufipes, Bembidion femoratum, Cilivina fossor, turned out to be the most voracious. The least amount of gluttony was noted in Bembidion quadrimaculatum. Four-pointed bembidion beetles killed an average of 7.33 eggs per day with 20 eggs, and with a density of 50 and 100 eggs, 14 and 27.66 eggs, respectively. However, it should be noted that under natural conditions, large species are less willing to eat eggs, in comparison with small species, preferring larger victims.